A review and meta-analysis of the impact of intestinal worms on child growth and nutrition

Hall A, Hewitt G, Tuffrey V, de Silva N

CRD summary

This review concluded that treating intestinal nematode worms in children leads to significant improvements in weight gain and growth. However, the pooling of studies exhibiting large degrees of both clinical and statistical heterogeneity, the lack of reporting of the review process, and the limitations of the available evidence, means the authors' conclusions should be treated with caution.

Authors' objectives

To assess the impact of intestinal worms on child growth and nutrition. This abstract will focus on the effect of treating intestinal worms on these outcomes.

Searching

MEDLINE, the reference lists of identified papers, a Cochrane review and a book were searched for English language papers. Search terms, but not dates, were reported. One unpublished study known to the author was also identified.

Study selection

Randomised controlled trials (RCTs) evaluating the use of anthelmintic alone compared to an untreated control group in young people (aged 1-19 years), with at least 12 weeks follow-up, were eligible for inclusion. Trials were also required to be conducted in areas where the initial prevalence of infection with any nematode worm was at least 50% and report data for one of a range of pre-specified outcomes as a mean with standard deviation (SD) and sample size or sufficient detail to calculate a SD. Most of the included studies evaluated albendazole, with levamisole, mebendazole, piperazine and pyrantel pamoate also evaluated. Details of the regimes were reported. Where reported, the age of participants ranged from 1-16 years, the prevalence of Ascaris from 18-100%, Trichuris 5-100% and hookworm 0-96%. Half of the studies were conducted in Africa.

The authors did not state how studies were selected for the review or how many reviewers performed the selection.

Assessment of study quality

Trials were rejected if the control group or method of allocation were inadequate. There was no detail as to how decisions were made and no further quality assessment was undertaken.

Data extraction

Mean differences for each outcome were extracted from each trial, with SD either extracted or calculated from confidence intervals (CI). Data for urban and rural children were extracted seperately from one trial.

The authors did not state how many reviewers performed the data extraction.

Methods of synthesis

Weighted mean (WMD) or median differences and 95% CI were calculated using a fixed effect model. Data for mebendazole and albendazole were combined. Data for other drugs were analysed separately. Heterogeneity was assessed using the Χ2 and I2 tests.

Results of the review

Nineteen trials were included in the review (n=40,579; range 51 to 27,995).

Levamisole, piperazine and pyrantel were evaluated in one study each and showed varying results across outcomes; when combined with the studies of albendazole and mebendazole, the results generally reflected those reported for these two drugs.

Cost information

The cost per infected child treated is 6 US cents when prevalence is at 50%, 15 US cents when prevalence is at 20% and 60 US cents when prevalence is at 5%.

Authors' conclusions

Compared to controls, treatments for intestinal nematode worms can lead to significant improvements in weight gain and growth in children.

CRD commentary

The authors addressed a clear review question. However, the search was limited and publication bias cannot be ruled out. No details of the review process were reported, therefore it is not possible to assess the potential for error and bias. Two quality criteria were used during the selection of studies but no further quality assessment was conducted. The authors combined studies that exhibited large degrees of both clinical and statistical heterogeneity. This might not have been appropriate. Several of the studies were very small and only mebendazole and albendazole were evaluated in more than one study. Given the limitations of the evidence and the review, the authors' conclusions should be treated with caution.

Implications of the review for practice and research

Practice: The authors stated that there is justification for giving mass treatment to all pre-school children, women of child-bearing age in the second and third trimester, and at-risk adults at least once a year where prevalence is greater than 50%.

Research: The authors stated that further studies are required to evaluate the effectiveness of anthelmintics delivered through health programmes, especially those focussing on pre-school and school-age children. Concommitent use of multiple micronutrients during studies may be useful to eliminate vitamin and mineral deificiency that may limit catch-up growth.

Funding

World Bank through the International Centre for Diarrhoeal Disease Research, Bangladesh.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.